This invention relates to apparatus for detecting the quantities of a rotary member, which is suited to a system wherein various quantities, for example, the voltage and current of a field magnetic circuit in a brushless A.C. generator are measured without contact.
Prior-art apparatus of this type for application to the brushless A.C. generator has been as shown in FIG. 1. As is well known, the generator is a revolving field type generator. Referring to the figure, letter F denotes the field winding of the generator, numeral 1 a field voltage sensor, numeral 2 a field current sensor, numerals 3 and 4 sense amplifiers, numerals 5 and 6 frequency modulators, numeral 7 a frequency mixer/amplifier, and numeral 8 a transmitting antenna. These components are installed within the rotor of the generator. Numeral 9 designates a receiving antenna, numerals 10 and 11 frequency tuner/amplifiers, numerals 12 and 13 FM demodulators, and numerals 14 and 15 analog indicators.
In operation, the signals of the voltage and current sensors are respectively amplified to required levels by the amplifiers 3 and 4 and then modulated by the frequency modulators 5 and 6. In this case, the transmitting frequencies of the frequency modulators 5 and 6 are unequal. The two frequency-modulated transmission signals are mixed in the mixing transmitter 7, and the mixed signal is transmitted from the transmitting antenna 8. The electric wave is received by the digital receiving antenna 9 on the stationary side. The received signal is distributed by the two tuning receivers 10 and 11, and the distributed signals are demodulated onto the original voltage and current values by the FM demodulators 12 and 13. The voltage and current values are respectively indicated by the indicators 14 and 15.
Since the prior-art measuring apparatus is constructed as described above, the transmission of a plurality of items of data necessitates the individual transmitters and receivers for the respective items of data. This has led to such a disadvantage that the circuit arrangement is complicated to render the apparatus expensive and to render adjusting operations etc. troublesome.